Need to replace fuel door on 2004 colorado will not stay closed

There is a pressure sensor on top of the tank , The sensor at the evap canister is not a sensor , it is a evap vent solenoid . The thing under the alternator is the purge soleniod . You would need to remove the fuel tank to replace the fuel pressure sensor . How to troubleshoot an EVAP Pressure Sensor problem P0452 GM

Fuel door or cap issues? What problem?

check the button on the door jam, if the door is indeed closed, some are adjustable some have to be replaced.

take off all handles and knobs. Then look real close for screws in panel. (most door panels are held in with hidden push clips)
gently pull panel away from door

Usually this problem occurs when a particular cylinder coil fails. You can swap coils of cyl 5 with another and see if the misfire follows to the cylinder that you exchanged coils with.If it does that confirms that that coil has failed. If it stays on the same cylinder you may have a spark plug or fuel injector issue.

Open the door and grab that "accordion style " boot and wiggle it while pushing window switch. If the window starts working, you have a wiring problem somewhere in that area. If not you may have a bad switch.

The release cable is sticking or broken. To release the fuel door, open the trunk and pull off the fabric liner on the left side of the trunk. Behind this liner is the fuel door release cable; this cable leads to the fuel door and attaches with a twist-lock connector. It is cylindrical with two tabs. Twist the connector clockwise about 90 degrees and it should pull out, releasing the door.

Just remember, the fuel door will not stay closed until you put the connector back in.

Spark plugs at 100,000 (use AC Delco plugs, they work best), check air filter at 15,000 replace at 30,000, replace fuel filter at 30,000, service (fluid and new filter) automatic trans at 60,000, replace hoses and flush cooling system at 100,000 miles, (use long life coolant), check belt at 30,000, replace if any rubber in ribs is missing, cracks are ok per factory bulletin's. oil and filter at least every 5,000 miles, lube chassis every other oil change, more often if u drive short trips, lube the door hinges and hood hinges and all latches every 30,000 miles. If I missed anything you want to know let me know. one last note manual trans and differential change lube only if torn down for repair, otherwise it is lifetime.

Since the passenger door doesn't get used as much as the drivers door, check to see if the switch is not just stuck. It is a little button with a spring that opens up and turns the light on. It is located on the hinge area of the door and when the door closes it shuts off the switch, if it is not stuck then I would suspect said switch.

Your battery is getting empty.